What is sudden sensorineural hearing loss?

SSHL is defined as a loss of 30 dB or more in three connected frequencies, occurring within 72 hours. It typically affects only one ear. Many people notice it when they wake up in the morning, or when they try to use the phone and realize they cannot hear out of one ear. It is often accompanied by a feeling of fullness in the ear, tinnitus (ringing), or dizziness.

SSHL affects approximately 5–27 people per 100,000 annually in the United States, though the true incidence may be higher because many cases go unreported or are misdiagnosed as earwax or congestion.

Causes

In about 85–90% of cases, no definitive cause is identified (idiopathic SSHL). When a cause is found, it may include:

• Viral infection: Viruses such as herpes simplex, mumps, measles, and COVID-19 have been associated with SSHL.
• Vascular events: Reduced blood flow to the cochlea, similar to a stroke in the inner ear.
• Autoimmune inner ear disease: The immune system attacks the inner ear.
• Acoustic neuroma: A benign tumor on the auditory nerve — SSHL is sometimes the first symptom.
• Perilymph fistula: A tear in the membrane separating the middle and inner ear.
• Ototoxic medications: Certain drugs can cause sudden hearing loss as a side effect.
• Meniere's disease: Sudden hearing loss can occur during Meniere's episodes.

Why the 72-hour window matters

The cochlea is highly sensitive to inflammation and reduced blood flow. Corticosteroids — the primary treatment for SSHL — work by reducing inflammation and suppressing immune activity in the inner ear. Their effectiveness drops significantly after the first 72 hours. Studies show that:

• About 32–65% of patients treated promptly recover some or all of their hearing.
• Spontaneous recovery (without treatment) occurs in about 32–65% of cases, but treatment improves outcomes.
• Delayed treatment substantially reduces the chance of recovery.

Diagnosis

An audiogram is essential to confirm SSHL and rule out conductive causes (like earwax). An MRI with gadolinium contrast is typically ordered to rule out acoustic neuroma. Blood tests and other imaging may be performed to look for underlying causes.

Treatment

Oral corticosteroids

High-dose oral prednisone is the standard first-line treatment, typically given for 10–14 days with a taper. It is most effective when started within 72 hours of onset.

Intratympanic steroid injections

Steroids injected directly through the eardrum into the middle ear space can deliver higher concentrations to the cochlea with fewer systemic side effects. This is used as a first-line treatment in patients who cannot take oral steroids, or as salvage therapy when oral steroids fail.

Hyperbaric oxygen therapy

Some evidence supports hyperbaric oxygen (HBO) as an adjunct treatment, particularly when started within two weeks of onset. It increases oxygen delivery to the cochlea.

If hearing does not recover

If significant hearing loss persists after treatment, hearing aids or cochlear implants can restore functional hearing. Many people with unilateral SSHL use a CROS hearing aid system or a bone-anchored device.

Prognosis

Outcomes vary widely. Factors associated with better recovery include younger age, less severe initial loss, absence of vertigo, and prompt treatment. Even with partial recovery, many people adapt well with appropriate hearing technology and audiological support.